2022 BDS Chem Prelims P1

This paper consists of 13 printed pages including this cover page BEDOK SOUTH SECONDARY SCHOOL PRELIMINARY EXAMINATION 2022 4EXP CANDIDATE NAME CLASS REGISTER NUMBER CHEMISTRY Additional Materials: Optical Mark Sheet (OMS) 6092/01 31st August 2022 1 hour READ THESE INSTRUCTIONS FIRST Write your class, register number and name on this paper with a blue or black pen. Write your name, register number, class and subject on the Optical Mark Sheet (OMS) provided. Write in soft pencil on the OMS. Do not use staples, paper clips, glue, or correction fluid. There are forty questions on this paper. Answer all questions. For each question, there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate OMS. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this paper. The use of an approved scientific calculator is expected, where appropriate. A copy of the Periodic Table is printed on page 13. For Examiner’s Use Paper 1 (30%) 40 Setter: DL ��

2 1 An unknown white solid, X, melts between 161 oC and 163 oC. When chromatography is performed with water as the solvent, X produces only one spot on the chromatogram. Which statement must be true about X? A X is pure. B X is impure. C X can sublime. D X is an ionic compound. 2 The boiling points of some substances found in air are given in the table. Air is cooled to -190 oC so that some of the substances in it condense. As the temperature is raised from -190 oC, which substance will undergo a change of physical state into a gas first? substance boiling point / oC A argon -186 B oxygen -183 C nitrogen -196 D carbon dioxide -78.5 3 Which statement correctly describes the rate and volume of hydrogen gas produced when 10 cm3 of 1.00 mol/dm3 of nitric acid and 10 cm3 of 1.00 mol/dm3 of ethanoic acid are reacted separately with excess magnesium until no visible reaction? volume of H2 produced rate of reaction A the same volume of H2 would be obtained for both acids The reaction with ethanoic acid would proceed at a slower rate B the volume of H2 would be more when nitric acid is used The reaction with ethanoic acid would proceed at a slower rate C the same volume of H2 would be obtained for both acids both reactions would proceed at the same rate D the volume of H2 would be more when nitric acid is used both reactions would proceed at the same rate ��

3 4 The rate of diffusion of different gases is measured at the same temperature and pressure. Which two gases would diffuse at a different rate? A N2 and CO B C2H4 and N2 C CO2 and C3H8 D C3H6 and CO 5 The Rf values for the dyes, J – M, in four different solvents are shown in the table. solvent water organic solvent 1 organic solvent 2 organic solvent 3 dye J 0.3 0.5 0.7 0.6 dye K 0.0 0.2 0.6 0.7 dye L 0.2 0.1 0.4 0.8 dye M 0.5 0.2 0.6 0.9 Which solvent could be used to separate a mixture of all four dyes, J, K, L and M? A water B organic solvent 1 C organic solvent 2 D organic solvent 3 6 An isotope of element X has 15 protons and 17 neutrons in its nucleus. Which chemical symbol best represents the ion of X? A X32153+ B X32153- C X15323+ D X15323- ��

4 7 Three different experiments that involve colour changes are carried out . 1 Universal Indicator solution is bubbled with ammonia gas. 2 Sulfur dioxide is tested with acidified potassium manganate(VII) solution. 3 Chlorine gas is bubbled into litmus solution. Which row correctly identifies the experiments that correspond to the colour changes? purple to colourless green to blue red to colourless A 2 1 3 B 2 3 1 C 3 1 2 D 1 2 3 8 Which of the following represents the most likely structural formula for the compound S2Cl2? A S – Cl – Cl – S B S – Cl – S – Cl C Cl – S – S – Cl D Cl = S – S = Cl 9 An imaginary element has two isotopes: • The first isotope has 15 protons and a relative abundance of 80% • The second isotope has 16 neutrons If the relative atomic mass of the imaginary element is 30.2, determine the number of neutrons in the first isotope. A 15 B 16 C 17 D 18 10 A book recorded the formula of a sample of rust as ‘2Fe2O3.𝟑𝟐H2O’. What is the percentage by mass of iron in this sample of rust? A 29.9% B 32.3% C 59.9% D 64.6% ��

5 11 What is the volume of carbon dioxide gas (at room temperature and pressure) produced when 2.65 g sodium carbonate reacts with 100 cm3 of 0.10 mol/dm3 hydrochloric acid? A 120 cm3 B 240 cm3 C 600 cm3 D 1200 cm3 12 In an electrolysis experiment, the same amount of charge deposited 6 g of titanium and 16 g of copper. The charge on the copper ion was 2+. [Ar: Ti, 48; Cu, 64] What was the charge on the titanium ion? A 1+ B 2+ C 3+ D 4+ 13 How many different ions are present in aqueous iron(II) sulfate? A 2 B 3 C 4 D 5 14 Which statement about ammonia is correct? A It reacts with alkalis to form salts. B It dissolves in water to form an acidic solution. C It is formed when ammonium salts are heated with sulfuric acid. D It decomposes on heating to a high temperature to form nitrogen and hydrogen. 15 Solid ammonium chloride decomposes on heating in a test tube to produce two gases. Which change would be observed to a piece of moist red litmus paper? A remains red B turns blue and remains blue C turns blue and then turns red D turns blue and then bleached ��

6 16 Which reagent cannot be used to distinguish aluminium hydroxide from calcium hydroxide? A ` H2SO4(aq) B HCl(aq) C NaOH(aq) D NH4OH(aq) 17 Salt X can be prepared by reacting together an acid and a metal or insoluble metal carbonate. A pure sample of salt X is then obtained by filtration, followed by crystallisation of the filtrate. What is the identify of salt X? A lead(II) sulfate B sodium chloride C copper(II) sulfate D magnesium chloride 18 Chlorine is reacted with aqueous potassium bromide and a brown solution is formed. Which statement about this reaction is correct? A Bromide ions gain electrons. B The oxidation state of chlorine decreases. C Chlorine is reduced because it loses electrons. D Bromine has a higher electron affinity than chlorine. 19 Lithium reacts with dilute nitric acid at a constant room temperature. Which statement about the rate of this reaction is correct? A It increases as the reaction proceeds. B It decreases as the reaction proceeds. C It remains the same as the reaction proceeds. D It increases then remains the same as the reaction proceeds. 20 An aqueous solution of sodium hydroxide has a pH of 10. Which substance could be added to the aqueous sodium hydroxide to increase the pH? A H+ ions B OH- ions C Na+ ions D H2O molecules 21 For which does 10 g of the metal have the most electrons in its sea of electrons’? A aluminium (Al) B sodium (Na) C lithium (Li) D magnesium (Mg) ��

7 22 Metal M can be obtained from its aqueous chloride by electrolysis and from its oxide by heating with carbon. Which metal is M? A sodium B silver C lead D copper 23 Potassium reacts with water to form solution R and gas S. When solution R reacts with dilute nitric acid, salt T is formed. What are the formulae of R, S and T? solution R gas S salt T A KOH H2 KNO3 B KOH CO2 K2NO3 C POH H2 PNO3 D POH CO2 P2NO3 24 A substance NaXO4 undergo a chemical reaction with hydrogen peroxide, according to the following equation: 2NaXO4 + 3H2O2 à 2XO2 + 2NaOH + 2H2O + 3O2 What is the role of hydrogen p